Electromagnetic quasi-zero stiffness vibration isolation device and method based on composite nested structure

Abstract

The application provides an electromagnetic quasi-zero stiffness vibration isolation device and method based on a composite nested structure, and belongs to the technical field of vibration isolation. The device comprises a supporting base, two linear induction motor assemblies symmetrically arranged on the base and provided with a preset gap, and a suspension support frame composed of a vertical conductive support plate and a horizontal magnetic conductive support plate. The vertical conductive support plate can float up and down in the gap and forms a positive stiffness module with the motor assembly to provide a main supporting force and positive stiffness. Two pairs of symmetrical electric eddy current stator pairs are distributed on the left and right sides of the horizontal magnetic conductive support plate and form a negative stiffness module with the horizontal magnetic conductive support plate to provide negative stiffness. Each pair of electric eddy current stator pairs comprises an upper electric eddy current stator assembly and a lower electric eddy current stator assembly which are mutually repulsive and float up and down on the left and right sides of the horizontal magnetic conductive support plate. The positive and negative stiffness modules are coaxially arranged and are connected in parallel through a composite nested structure to realize the quasi-zero stiffness characteristic. The application can realize dynamic stiffness adjustment, improve the vibration isolation effect and reliability.

Description

Technical Field

[0001] This invention relates to the field of low-frequency vibration isolation technology, and in particular to an electromagnetic quasi-zero stiffness vibration isolation device and method based on a composite nested structure. Background Technology

[0002] The vibration isolation performance of traditional linear vibration isolation devices relies on reducing stiffness. According to the principle of vibration isolation, the natural frequency of a linear system is proportional to the square root of its stiffness. The lower the stiffness, the lower the natural frequency, and the lower the lower limit of the vibration isolation frequency can be. However, this characteristic has an inherent contradiction: while reducing stiffness can expand the low-frequency vibration isolation range, it will lead to a decrease in the static load-bearing capacity of the system and an increase in static deformation; on the other hand, if the stiffness is increased to ensure the load-bearing capacity, the natural frequency will increase, making it impossible to effectively isolate low-frequency vibrations below 10Hz, thus creating a dilemma of load-bearing and vibration isolation.

[0003] To resolve this contradiction, quasi-zero stiffness (QZS) vibration isolation technology has emerged. Its core idea is to use a nonlinear combination of positive and negative stiffness to bring the overall system stiffness close to zero (quasi-zero stiffness state) near the static equilibrium position. This achieves both a low natural frequency to isolate low-frequency vibrations and maintains high static stiffness to suppress static deformation, thus meeting the ideal vibration isolation requirement of "high static stiffness and low dynamic stiffness".

[0004] Currently available quasi-zero stiffness vibration isolation devices are mainly divided into two categories: one is based on geometric nonlinear mechanical structures, such as using the bending deformation of inclined springs, cam-roller mechanisms or elastic beams to provide negative stiffness, which is combined with the positive stiffness of the main spring; the other is a purely electromagnetic device based on electromagnetic effects, which provides negative stiffness through the magnetic repulsion / magnetic attraction of permanent magnets or the electromagnetic force of electromagnetic coils, matching the positive stiffness of mechanical components.

[0005] However, existing technologies still have significant limitations. While geometrically nonlinear mechanical quasi-zero stiffness devices are simple in structure and highly reliable, their negative stiffness is determined by the geometry of the mechanical structure. Once manufactured, the stiffness characteristics are fixed and cannot be adjusted, making them unsuitable for scenarios with varying excitation frequencies or loads. Furthermore, limited by the deformation range of the mechanical structure, the quasi-zero stiffness working stroke is short, making it prone to vibration isolation failure due to vibration displacement exceeding the stroke. Although a single electromagnetic quasi-zero stiffness device can achieve dynamic control of negative stiffness by adjusting the coil current, when the coil fails, the negative stiffness disappears, the system instantly degenerates into a linear structure, low-frequency vibration isolation function is lost, and reliability redundancy is lacking, making it difficult to apply to scenarios with high safety requirements.

[0006] Therefore, there is an urgent need for an electromagnetic quasi-zero stiffness vibration isolation device and method based on a composite nested structure, which can achieve dynamic adjustment of stiffness and improve vibration isolation effect and reliability. Summary of the Invention

[0007] The purpose of this invention is to provide an electromagnetic quasi-zero stiffness vibration isolation device and method based on a composite nested structure, which aims to solve the technical problem that traditional quasi-zero stiffness vibration isolation devices are difficult to achieve good vibration isolation effect in a wide frequency range.

[0008] To achieve the above objectives, in a first aspect, the present invention provides an electromagnetic quasi-zero stiffness vibration isolation device based on a composite nested structure, comprising:

[0009] Support base;

[0010] Two linear induction motor assemblies are symmetrically arranged on the support base about the vertical central axis of the support base, and there is a preset gap between the two linear induction motor assemblies.

[0011] The suspended support frame includes a vertical conductive support plate and a horizontal magnetic support plate, wherein the horizontal magnetic support plate is horizontally positioned on top of the vertical conductive support plate;

[0012] The vertical conductive support plate is set in a preset gap between the two linear induction motor assemblies in a way that allows it to float up and down, and together with the two linear induction motor assemblies, it forms a positive stiffness module to provide the main support force and positive stiffness in the vertical direction.

[0013] Two pairs of eddy current stators are symmetrically arranged on the left and right sides of the horizontal magnetic support plate, and each pair of eddy current stators cooperates with the horizontal magnetic support plate to form a negative stiffness module, which is used to provide negative stiffness in the vertical direction.

[0014] Each pair of eddy current stators includes an upper eddy current stator assembly and a lower eddy current stator assembly. The upper eddy current stator assembly and the lower eddy current stator assembly are respectively floating on the upper and lower sides of the horizontal magnetic support plate and are in a mutually exclusive state.

[0015] The positive stiffness module and the negative stiffness module are arranged coaxially in the vertical direction and coupled to each other in the form of a composite nested structure, so that the positive stiffness module and the negative stiffness module work in parallel and cooperate to maintain the quasi-zero stiffness state of this vibration isolation device.

[0016] As a further improvement to the above solution, the horizontal magnetic support plate is also equipped with a displacement sensor, which is used to detect the vertical floating displacement of the suspended support frame and feed it back to the controller.

[0017] The controller adjusts the current magnitude of the linear induction motor assembly and / or eddy current stator pair in real time based on the received vertical floating displacement to maintain the near-zero stiffness state of the vibration isolation device.

[0018] As a further improvement to the above solution, the linear induction motor assembly includes a stator core and a three-phase AC winding embedded in the stator core.

[0019] An alternating current is passed through the three-phase AC windings, and the relatively arranged linear induction motor assembly generates a traveling wave magnetic field that interacts with the vertical conductive support plate to form a vertical electromagnetic thrust to provide the main support force and positive stiffness.

[0020] As a further improvement to the above solution, the vertical conductive support plate includes a vertical support plate body, vertical moving conductor conductive plates respectively attached to both sides of the vertical support plate body, and vertical moving magnetic plates respectively attached to the outer side of the corresponding vertical moving conductor conductive plates.

[0021] As a further improvement to the above solution, the horizontal magnetic support plate includes a horizontal support plate body, a first upper moving magnetic plate and a second upper moving magnetic plate respectively spaced and attached to the upper surface of the horizontal support plate body, and a first lower moving magnetic plate and a second lower moving magnetic plate respectively spaced and attached to the lower surface of the horizontal support plate body.

[0022] Furthermore, the upper moving element magnetic plate and the lower moving element magnetic plate are positioned in a matching manner.

[0023] The upper moving part magnetic plate and the lower moving part magnetic plate are positioned in a matching manner.

[0024] As a further improvement to the above scheme, the upper eddy current stator assembly and the lower eddy current stator assembly have the same structure, each including an eddy current stator core and a plurality of DC coil units disposed on the eddy current stator core, with each DC coil unit connected in parallel.

[0025] As a further improvement to the above scheme, in the initial equilibrium state, the upper eddy current stator assembly and the horizontal magnetic support plate have the same air gap, and the lower eddy current stator assembly and the horizontal magnetic support plate are in equilibrium.

[0026] When the load changes and causes the suspended support frame to move vertically, the upper and lower air gaps change differentially, resulting in an imbalance of electromagnetic attraction. The negative stiffness module generates a net restoring force that is opposite to the displacement trend. The relationship between the net restoring force and the displacement is characterized by negative stiffness.

[0027] As a further improvement to the above solution, the electromagnetic quasi-zero stiffness vibration isolation device also includes a load support platform, which includes a vertical support arm and a horizontal support platform disposed on the vertical support arm; the vertical support arm is connected to the middle of the upper surface of the horizontal magnetic support plate, and the horizontal support platform is used to support the load; and a gravity sensor is provided on the load support platform to detect the weight of the load.

[0028] As a further improvement to the above solution, the support base includes a base plate and two vertical plates vertically arranged on the base plate, with the two vertical plates spaced apart.

[0029] A linear induction motor assembly is disposed on the inner side of a vertical plate;

[0030] Another linear induction motor assembly is correspondingly disposed on the inner side of another vertical plate, so that the two linear induction motor assemblies are arranged opposite each other.

[0031] In a second aspect, the present invention also provides a control method for an electromagnetic quasi-zero stiffness vibration isolation device based on a composite nested structure as described in the first aspect, the steps of which include:

[0032] S1. Initial alternating current is passed through the three-phase AC windings of the two linear induction motor components to generate an upward electromagnetic repulsive force F. The balance between F and the load gravity mg is monitored by a force sensor. The amplitude of the alternating current is finely adjusted to F=mg, and the device establishes initial positive stiffness to stably support the load.

[0033] S2. Simultaneously apply initial DC current to the upper and lower eddy current stator components in each pair of eddy current stators. Feedback is obtained from the displacement sensor regarding the mechanical air gap between the upper and lower eddy current stator components and the horizontal magnetic support plate. The DC current is finely adjusted to ensure that the horizontal magnetic support plate is in the middle position between the upper and lower eddy current stator components and has an initial preset mechanical air gap d.

[0034] S3. The displacement sensor acquires the vertical displacement x of the horizontal magnetic support plate in real time, and the force sensor collects the load change in real time, and feeds it back to the controller. The controller adjusts the current of the linear induction motor assembly and / or the eddy current stator pair in real time according to the received vertical displacement x and load to maintain the quasi-zero stiffness state of the vibration isolation device.

[0035] As a further improvement to the above scheme, in step S3, when the load increases, the electromagnetic repulsion of the positive stiffness module is increased by increasing the three-phase AC winding current of the linear induction motor assembly to support the new load and return the vertical conductive support plate to the static equilibrium position; at the same time, the DC current of the eddy current stator pair is increased to enhance the electromagnetic force of the negative stiffness module, and the positive stiffness module works together to maintain the quasi-zero stiffness state.

[0036] When the load decreases, the electromagnetic repulsion of the positive stiffness module is reduced by decreasing the three-phase AC winding current of the linear induction motor assembly to support the reduced load and return the vertical conductive support plate to its static equilibrium position; at the same time, the DC current of the eddy current stator pair is reduced to reduce the electromagnetic force of the negative stiffness module, and together with the positive stiffness module, the quasi-zero stiffness state is maintained.

[0037] Because the present invention adopts the above technical solutions, the beneficial effects of this application are as follows:

[0038] 1. This invention provides an electromagnetic quasi-zero stiffness vibration isolation device based on a composite nested structure. A positive stiffness module (linear induction motor assembly and vertical conductive support plate) provides the main support force and static stiffness, while a negative stiffness module (eddy current stator pair and horizontal magnetic support plate) generates dynamic negative stiffness. The two modules are coaxially nested and work in parallel to achieve a system overall stiffness close to zero, thus achieving an effective balance between static load-bearing and dynamic vibration isolation performance. It provides stable support for equipment weight under static conditions and significantly reduces the system's equivalent stiffness under dynamic conditions, specifically addressing the inherent contradiction of insufficient vibration isolation performance in the low-frequency range of traditional linear vibration isolation structures.

[0039] Compared to mechanical quasi-zero stiffness structures such as spring-type, spring-linkage type, and cam-roller-spring type, this invention uses electromagnetic force to achieve non-contact support, fundamentally eliminating secondary vibration interference caused by mechanical friction, wear, and contact fatigue, thus improving the reliability and service life of the device. Addressing the limitation of poor load adaptability in passive quasi-zero stiffness devices, this invention precisely controls the magnitude of positive and negative stiffness electromagnetic forces by real-time adjustment of the current between the linear induction motor and the eddy current stator pair, achieving dynamic stiffness adjustment. It can adapt to different loads and vibration frequencies without disassembly, significantly enhancing applicability and flexibility. Furthermore, the electromagnetic force response reaches the millisecond level, rapidly suppressing sudden vibration impacts.

[0040] In some preferred embodiments, the upper eddy current stator assembly and the lower eddy current stator assembly have the same structure, each including an eddy current stator core and a plurality of DC coil units disposed on the eddy current stator core, with each DC coil unit connected in parallel. The present invention suppresses nonlinear interference by optimizing the magnetic pole layout and improves reliability by adopting a redundant design of multiple DC coil units, ensuring that stable quasi-zero stiffness characteristics and excellent vibration isolation performance are maintained under wideband excitation.

[0041] 2. This invention also provides a control method for an electromagnetic quasi-zero stiffness vibration isolation device based on a composite nested structure. By adjusting the three-phase AC current in real time through a linear induction motor assembly, the balance between the electromagnetic repulsion force F and the load gravity mg is dynamically controlled, achieving on-demand adjustment of the positive stiffness. Combined with an eddy current stator pair, the mechanical air gap d is adjusted via DC current to actively control the electromagnetic force of the negative stiffness module. The synergy of these two methods allows the device to maintain a quasi-zero stiffness state through current feedback adjustment when the load changes, thus solving the technical problem of unadjustable stiffness in traditional vibration isolation devices. The composite nested structure decouples the positive and negative stiffness, allowing for independent current control to adapt to different load ranges. The eddy current effect of the negative stiffness module further reduces the system's natural frequency due to the lack of mechanical contact. Combined with the positive stiffness module, this effectively extends the vibration isolation frequency band, especially for low-frequency vibrations that are difficult to suppress with traditional devices. Real-time feedback from displacement and force sensors forms a dual closed-loop regulation, and the accuracy of current adjustment is directly related to the stiffness balance state. Compared to open-loop vibration isolators, this invention reduces stiffness drift caused by environmental interference and improves long-term operational reliability through a closed-loop link of sensor-controller-actuator (linear induction motor assembly / eddy current stator pair). Attached Figure Description

[0042] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0043] Figure 1 This is a front view schematic diagram of an electromagnetic quasi-zero stiffness vibration isolation device based on a composite nested structure disclosed in this invention;

[0044] Figure 2 This is a front view schematic diagram of an electromagnetic quasi-zero stiffness vibration isolation device based on a composite nested structure (without the support base and load support platform) disclosed in this invention;

[0045] Figure 3 for Figure 2 A side view diagram;

[0046] Figure 4 for Figure 2 A three-dimensional schematic diagram;

[0047] Figure 5 This is a front view schematic diagram of the negative stiffness module;

[0048] Figure 6 This is a front view schematic diagram of a vertical conductive support plate;

[0049] Figure 7This is a front view schematic diagram of a linear induction motor assembly;

[0050] Figure 8 A three-dimensional schematic diagram of an upper-energized eddy current stator assembly or a lower-energized eddy current stator assembly;

[0051] Figure 9 This is a schematic diagram of the negative stiffness module implementation of an electromagnetic quasi-zero stiffness vibration isolation device based on a composite nested structure disclosed in this invention.

[0052] Figure 10 This is a schematic diagram of the quasi-zero stiffness range of an electromagnetic quasi-zero stiffness vibration isolation device based on a composite nested structure disclosed in this invention.

[0053] Figure 11 This is a schematic diagram of the working process of an electromagnetic quasi-zero stiffness vibration isolation device based on a composite nested structure disclosed in this invention.

[0054] Figure label:

[0055] 1. Support base; 11. Base plate; 12. Vertical plate; 2. Linear induction motor assembly; 21. Stator core; 22. Three-phase AC winding; 3. Suspension support frame; 31. Vertical conductive support plate; 311. Vertical support plate body; 312. Vertical mover conductive plate; 313. Vertical mover magnetic plate;

[0056] 32. Horizontal magnetic support plate; 321. Horizontal support plate body; 322. First upper moving part magnetic plate; 323. Second upper moving part magnetic plate; 324. First lower moving part magnetic plate; 325. Second lower moving part magnetic plate;

[0057] 4. Eddy current stator pair; 41. Upper eddy current stator assembly; 42. Lower eddy current stator assembly; 411. Eddy current stator core; 412. DC coil unit; 5. Load support platform; 51. Vertical support arm; 52. Horizontal support platform.

[0058] The objectives, features, and advantages of this invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0059] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0060] It should be noted that all directional indicators (such as up, down, etc.) in the embodiments of the present invention are only used to explain the relative positional relationship and movement of each component in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indicator will also change accordingly.

[0061] Furthermore, in this invention, descriptions involving "first," "second," etc., are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include at least one of that feature.

[0062] Furthermore, the technical solutions of the various embodiments of the present invention can be combined with each other, but only if they are based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by the present invention.

[0063] Example 1

[0064] See Figures 1-10 This invention provides an electromagnetic quasi-zero stiffness vibration isolation device based on a composite nested structure, comprising: a support base 1, two linear induction motor assemblies 2, a suspended support frame 3, and two pairs of eddy current stators 4. The components are combined according to a specific spatial layout and mechanical relationship. Through the composite nesting and parallel coupling of positive stiffness modules and negative stiffness modules, the system achieves quasi-zero stiffness characteristics in the vertical direction, thereby improving vibration isolation performance. Specifically:

[0065] Support base 1, the support base 1 includes a base plate 11 and two vertical plates 12 vertically arranged on the base plate 11, and the two vertical plates 12 are spaced apart;

[0066] Two linear induction motor assemblies 2 are symmetrically arranged on the upper surface of the support base 1 with the vertical central axis of the support base 1 as the axis of symmetry. Specifically, one linear induction motor assembly 2 is disposed on the inner side of one vertical plate 12, and the other linear induction motor assembly 2 is disposed on the inner side of another vertical plate 12, so that the two linear induction motor assemblies 2 are arranged opposite each other and a certain preset gap is maintained between them. The preset gap is used to accommodate the vertical conductive support plate 31 in the subsequent suspension support frame 3, so that it can float up and down within a certain range in the vertical direction. Each linear induction motor assembly 2 includes a stator core 21 and a three-phase AC winding 22 embedded in the stator core 21. The stator core 21 is fixed on the support base 1. In this embodiment, the outer sides of the two stator cores 21 are respectively fixed to the corresponding vertical plates 12 by screws, and their bottoms are fixed to the base plate 11 by screws.

[0067] The suspended support frame 3 is a key structure connecting the vibration-isolated object with the positive stiffness module and the negative stiffness module, and it includes:

[0068] The vertical conductive support plate 31 is a vertically arranged conductive plate. The vertical conductive support plate 31 is arranged in a preset gap between two linear induction motor assemblies 2 in a way that allows it to float up and down. Together with the two linear induction motor assemblies 2, it forms a positive stiffness module. When alternating current is passed into the three-phase AC winding 22, the relatively arranged linear induction motor assemblies 2 generate a traveling wave magnetic field and interact with the vertical conductive support plate 31 to form a vertical electromagnetic thrust to provide the main support force and positive stiffness.

[0069] The horizontal magnetic support plate 32 is a horizontally placed magnetic flat plate, which is fixed to the top of the vertical conductive support plate 31. It is used to support the object to be isolated from vibration and also serves as the working surface of the eddy current negative stiffness module.

[0070] Two pairs of eddy current stators 4 are symmetrically arranged on the left and right sides of the horizontal magnetic support plate 32. Each pair of eddy current stators 4 includes an upper eddy current stator assembly 41 and a lower eddy current stator assembly 42. The upper eddy current stator assembly 41 is located above the horizontal magnetic support plate 32, forming an upper air gap with the horizontal magnetic support plate 32. The lower eddy current stator assembly 42 is located below the horizontal magnetic support plate 32, forming a lower air gap with the horizontal magnetic support plate 32. The upper eddy current stator assembly 41 and the lower eddy current stator assembly 42 form an upper air gap with the horizontal magnetic support plate 32. The eddy current stator assemblies 42 are structurally independent, but mechanically they are mutually exclusive. That is, when the horizontal magnetic support plate 32 is displaced, the upper eddy current stator assembly 41 and the lower eddy current stator assembly 42 generate eddy current effects in the vicinity of the horizontal magnetic support plate 32 through relative movement with it, thereby forming magnetic resistance opposite to the displacement direction, which manifests as negative stiffness characteristics. Each pair of eddy current stators 4 cooperates with the horizontal magnetic support plate 32 to form a negative stiffness module, which is used to provide negative stiffness in the vertical direction.

[0071] The positive stiffness module and the negative stiffness module are arranged coaxially in the vertical direction in a composite nested structure, achieving parallel coupling between them. Specifically:

[0072] Both the positive stiffness module and the negative stiffness module are configured vertically, and their central axes coincide, ensuring that they act in the same displacement direction, i.e., the vertical direction, in terms of mechanical response. The vertical conductive support plate 31 is located in the preset gap between the two linear induction motor assemblies 2, while the horizontal magnetic support plate 32 is located above the vertical conductive support plate 31 and maintains an appropriate air gap with the eddy current stator pairs 4 on both sides. This spatial layout allows the positive and negative stiffness action areas to be nested in the vertical direction, forming a tight structural coupling.

[0073] During operation, the positive stiffness module provides a positive restoring force that increases with displacement, while the negative stiffness module provides a negative restoring force that increases with displacement but at a slower rate. Both modules work together in parallel on the suspended support frame 3, ensuring that at a specific equilibrium position, the resultant force of the positive and negative stiffnesses approaches zero, thus achieving a quasi-zero stiffness state for the system. In this quasi-zero stiffness state, the response to minute external excitations is significantly reduced, resulting in a significant improvement in vibration isolation. Precise control of the positive and negative stiffness values ​​can be achieved by adjusting the current of the linear induction motor assembly 2, the air gap size, or the configuration parameters of the eddy current stator pair 4, thereby adapting to different vibration isolation requirements.

[0074] When an external excitation is applied to the vibration-isolated object, the suspended support frame 3 will cause the vertical conductive support plate 31 and the horizontal magnetic support plate 32 to undergo vertical displacement. At this time:

[0075] The linear induction motor assembly 2 generates a corresponding electromagnetic force according to the displacement of the vertical conductive support plate 31, forming a positive stiffness support to prevent the support frame from sinking or floating excessively.

[0076] At the same time, the horizontal magnetic support plate 32 is displaced relative to the eddy current stator pairs 4 on both sides, which triggers the eddy current effect and generates magnetic resistance in the opposite direction of displacement, thus forming a negative stiffness effect.

[0077] Positive stiffness and negative stiffness act in parallel in the vertical direction. Through reasonable design, they cancel each other out within a certain displacement range, achieving a near-zero stiffness equilibrium state, thereby effectively isolating external low-frequency vibrations.

[0078] The electromagnetic quasi-zero stiffness vibration isolation device based on a composite nested structure provided by this invention provides the main support force and static stiffness through a positive stiffness module (linear induction motor assembly 2 and vertical conductive support plate 31), and generates dynamic negative stiffness through a negative stiffness module (eddy current stator pair 4 and horizontal magnetic support plate 32). The two modules are coaxially nested and work together in parallel to make the overall stiffness of the system approach zero, thereby achieving an effective balance between static load bearing and dynamic vibration isolation performance. It can stably support the weight of the equipment in static conditions and significantly reduce the equivalent stiffness of the system in dynamic conditions, thus specifically solving the inherent contradiction of insufficient vibration isolation performance of traditional linear vibration isolation structures in the low-frequency range.

[0079] Compared to mechanical quasi-zero stiffness structures such as spring-type, spring-linkage type, and cam-roller-spring type, this invention uses electromagnetic force to achieve non-contact support, fundamentally eliminating secondary vibration interference caused by mechanical friction, wear, and contact fatigue, thus improving the reliability and service life of the device. Addressing the limitation of poor load adaptability in passive quasi-zero stiffness devices, this invention precisely controls the magnitude of positive and negative stiffness electromagnetic forces by real-time adjustment of the current in the linear induction motor and eddy current stator pair 4, achieving dynamic stiffness adjustment. It can adapt to different loads and vibration frequencies without disassembly, significantly enhancing applicability and flexibility. Furthermore, the electromagnetic force response is at the millisecond level, rapidly suppressing sudden vibration impacts.

[0080] In a preferred embodiment, a displacement sensor (not shown in the figure) is provided on the horizontal magnetic support plate 32 to detect the floating displacement of the suspension support frame 3 in the vertical direction in real time. The displacement sensor can typically employ a non-contact measurement method, such as a laser displacement sensor or a magnetostrictive displacement sensor. The sensor signal output is connected to a subsequent controller to provide real-time displacement feedback information.

[0081] The controller receives real-time displacement signals from the displacement sensors and calculates the current displacement state of the suspension support 3 based on these signals. According to the set control algorithm (such as PID control, fuzzy control, or other feedback control strategies), the controller determines whether the actual stiffness state of the current system deviates from the quasi-zero stiffness point. If a deviation from the target equilibrium position is detected, the controller will adjust one or more of the following control parameters in real time:

[0082] Adjusting the power supply current of the two linear induction motor assemblies 2 changes the electromagnetic force they generate, thereby adjusting the restoring force of the positive stiffness module.

[0083] Alternatively, the supply current of the two pairs of eddy current stators 4 can be adjusted to change the intensity of the eddy current effect, thereby adjusting the force of the negative stiffness module.

[0084] Alternatively, the currents of the linear induction motor assembly 2 and the eddy current stator pair 4 can be adjusted simultaneously to achieve coordinated control of positive and negative stiffness.

[0085] Through the above control methods, the controller can dynamically compensate for stiffness deviations caused by external disturbances, load changes, or system parameter drift, so that the system always maintains or approaches the quasi-zero stiffness operating point, thereby improving the stability and reliability of vibration isolation effect.

[0086] During operation, when the suspended support frame 3 experiences vertical displacement due to external vibration excitation, the displacement sensor captures the displacement signal in real time and transmits it to the controller. The controller, based on its built-in control logic, calculates the required compensation current value and adjusts the current of the linear induction motor assembly 2 and / or the eddy current stator pair 4 via the drive circuit. By adding a displacement sensor and controller, and introducing a feedback-based current control mechanism, the adaptive capability and control accuracy of this vibration isolation device are further enhanced. This allows the vibration isolation system to dynamically adjust according to actual working conditions, improving its adaptability to different loads and excitation frequencies, making it particularly suitable for applications requiring high vibration isolation accuracy.

[0087] In a preferred embodiment, the vertical conductive support plate 31 comprises the following three-layer composite structure:

[0088] The vertical support plate body 311, as the main load-bearing structure, is generally made of conductive material with a certain mechanical strength to play a structural support and connection role.

[0089] Vertical moving part conductive plates 312 are respectively attached to two opposite sides of the vertical support plate body 311, namely the left and right sides. The vertical moving part conductive plates 312 are usually made of highly conductive materials. Their function is to participate in the electromagnetic induction process when interacting with the stator of the linear induction motor, and they are an important component in realizing positive stiffness support.

[0090] The vertical moving magnetic plate 313 is respectively attached to the outer surface of the vertical moving conductive plate 312 on the corresponding side, that is, it is closely attached to the vertical moving conductive plate 312 and tightly attached to it. It is usually made of a material with good magnetic permeability. Its function is to guide the magnetic field distribution, improve the efficiency of electromagnetic force, and enhance the coupling performance with the surrounding magnetic field components.

[0091] Specifically, when alternating current is applied to the three-phase AC winding 22 of the linear induction motor assembly 2, according to the principles of electromagnetism, the alternating current generates an alternating magnetic field around the stator core 21 that varies sinusoidally. This alternating magnetic field propagates in space at a certain speed along a straight line, similar to the rotation of the magnetic field in a rotating electrical machine, and is called a traveling wave magnetic field in a linear induction motor. The vertical conductive support plate 31, located between the two opposing linear induction motor assemblies 2, is situated within this traveling wave magnetic field. Due to the relative motion between the traveling wave magnetic field and the vertical conductive support plate 31, the vertical conductive support plate 31 cuts magnetic field lines, and according to the law of electromagnetic induction, an induced electromotive force is generated in the vertical conductive support plate 31. Furthermore, because the vertical conductive support plate 31 itself forms a conductive loop, an induced current is generated in the vertical conductive support plate 31 under the influence of the induced electromotive force.

[0092] The induced current generated in the vertical conductive support plate 31 produces a new magnetic field around it. According to Ampere's law, this magnetic field generated by the induced current interacts with the traveling wave magnetic field generated by the stator core 21 in the linear induction motor assembly 2, thus subjecting the vertical conductive support plate 31 to an Ampere force. By rationally designing the current direction and number of turns of the stator core 21 winding in the linear induction motor assembly 2, as well as the material and shape of the vertical moving conductor plate 312, the direction of the Ampere force can be controlled, making it exhibit a repulsive force in the vertical direction. When external vibration excitation causes relative displacement of related components, this repulsive force in the vertical direction can resist the displacement change, providing positive stiffness characteristics to the device. Working in conjunction with the negative stiffness structure, it achieves a quasi-zero stiffness vibration isolation effect.

[0093] like Figures 1-4 As shown, the positive stiffness is achieved based on the vertical electromagnetic repulsion generated between the two linear induction motor assemblies 2 and the vertical conductive support plate 31. When the load gravity mg acts on the load support platform 5, energizing the three-phase AC winding 22 generates an upward electromagnetic thrust F between the relatively arranged linear induction motor assemblies 2 and the vertical conductive support plate 31. At the static equilibrium position, F and mg are equal in magnitude but opposite in direction, and the system is in a stable state.

[0094] When the load deviates from its static equilibrium position due to external disturbances, if the vertical conductive support plate 31 moves upward, the coverage length at the static equilibrium position (the length of the linear induction motor assembly 2 covering the vertical conductive support plate 31) decreases, and the electromagnetic thrust F decreases. At this time, mg > F, and the weight of the load will cause the vertical conductive support plate 31 to tend to return to the static equilibrium position downward. If the vertical conductive support plate 31 moves downward, the coverage length increases, causing F to increase, and F > mg. The electromagnetic thrust will push the vertical conductive support plate 31 upward back to the static equilibrium position. This characteristic of generating a restoring force that causes the system to return to its equilibrium position when it deviates from the equilibrium position reflects the principle of positive stiffness, ensuring that the system has stable mechanical properties near the equilibrium position, effectively supporting the load and resisting small-scale disturbances.

[0095] In a preferred embodiment, the horizontal magnetic support plate 32 also adopts a multi-layer composite structure, including:

[0096] The horizontal support plate body 321, as the main structure of the component, is generally made of high-strength magnetic conductive material, used to support the object to be isolated from vibration, and as the magnetic field action surface of the eddy current negative stiffness module.

[0097] The first upper moving magnetic plate 322 and the second upper moving magnetic plate 323 are respectively attached to the upper surface of the horizontal support plate body 321 in a spaced manner. A certain distance is maintained between the two magnetic plates to avoid mutual interference, while achieving a uniform magnetic field distribution and effect.

[0098] The first lower moving magnetic plate 324 and the second lower moving magnetic plate 325 are respectively attached to the lower surface of the horizontal support plate body 321 at intervals. Their arrangement corresponds to the first upper moving magnetic plate 322 and the second upper moving magnetic plate 323, and satisfy the following positional relationship:

[0099] The first upper moving stator magnetic plate 322 and the first lower moving stator magnetic plate 324 are matched in the vertical direction, that is, aligned vertically, to ensure that a stable air gap and magnetic field coupling are formed between them and the eddy current stator assembly above or below.

[0100] The second upper moving stator magnetic plate 323 and the second lower moving stator magnetic plate 325 are also matched in the vertical direction, forming a corresponding magnetic field action area with the corresponding eddy current stator assembly.

[0101] Through layered and symmetrical arrangement, the horizontal magnetic support plate 32 can provide a uniform and matched magnetic working surface for the upper and lower eddy current stator assemblies 42, which helps to improve the spatial consistency of the eddy current effect, thereby enhancing the working stability and response accuracy of the negative stiffness module.

[0102] The upper eddy current stator assembly 41 and the lower eddy current stator assembly 42 are structurally identical, both including:

[0103] Eddy current stator core 411: It is usually made of soft magnetic material with high permeability and low loss, and is used to guide and concentrate magnetic field;

[0104] Several DC coil units 412 are wound or fixed on the eddy current stator core 411 to generate a stable magnetic field after energization. These DC coil units 412 are connected in parallel to reduce the current load of individual coils while ensuring a constant total current, thereby improving system reliability and thermal stability, and facilitating control and drive. The redundant design of multiple DC coil units 412 enhances reliability and ensures stable quasi-zero stiffness characteristics and excellent vibration isolation performance even under wideband excitation.

[0105] The upper and lower eddy current stator components 42 of the present invention can generate a stable magnetic field when energized, and induce eddy current effect when relative displacement occurs with the horizontal magnetic support plate 32, thereby forming magnetic resistance opposite to the displacement direction and realizing negative stiffness characteristics.

[0106] In the initial equilibrium state, see Figure 9When there is no external disturbance or load change, the upper eddy current stator assembly 41 and the horizontal magnetic support plate 32, as well as the lower eddy current stator assembly 42 and the horizontal magnetic support plate 32, maintain the same air gap d, and the electromagnetic attraction forces generated by the upper and lower stator assemblies are balanced in the vertical direction, so the system is in a stable equilibrium position. The upper eddy current stator assembly 41 generates an upward electromagnetic attraction force F2 on the horizontal magnetic support plate 32, and the lower eddy current stator assembly 42 generates a downward electromagnetic attraction force F1 on the horizontal magnetic support plate 32. In the initial equilibrium state, F1 and F2 are equal in magnitude, the net force on the horizontal magnetic support plate 32 is zero, and it remains stable and stationary.

[0107] When the load on the vibration-isolated object changes due to external excitation or internal factors, the suspension support frame 3 will undergo a vertical displacement x. The mechanical air gap between the horizontal magnetic support plate 32 and the upper eddy current stator assembly 41 becomes dx, and the mechanical air gap between the horizontal magnetic support plate 32 and the lower eddy current stator assembly 42 becomes d+x, meaning the sizes of the upper and lower air gaps are no longer equal. According to the relationship between electromagnetic attraction and mechanical air gap (the magnitude of electromagnetic attraction increases as the air gap decreases and decreases as the air gap increases), the electromagnetic attraction F2 of the upper eddy current stator assembly 41 on the horizontal magnetic support plate 32 will increase, while the electromagnetic attraction F1 of the lower eddy current stator assembly 42 on the horizontal magnetic support plate 32 will decrease. As F2 increases and F1 decreases, the horizontal magnetic support plate 32 will experience a resultant force opposite to the displacement x-direction (if the horizontal magnetic support plate 32 displaces upward, F2>F1, and the resultant force is downward; if the horizontal magnetic support plate 32 displaces downward, F1>F2, and the resultant force is upward). This resultant force can counteract the displacement trend caused by vibration excitation, thereby achieving a quasi-zero stiffness vibration isolation effect and effectively isolating vibrations transmitted from the outside. This imbalance of attraction will form a net restoring force in the vertical direction opposite to the displacement trend.

[0108] The magnitude of the net restoring force changes with increasing displacement, but its trend is that the larger the displacement, the smaller the increment of the restoring force, exhibiting negative stiffness characteristics. Through this mechanism, the negative stiffness module can suppress the displacement trend of the suspension support frame 3, working together with the positive stiffness module to achieve a quasi-zero stiffness state of the system near a specific equilibrium point. This setting makes the response of the negative stiffness module more direct and controllable, which is beneficial to improving the adaptive capability and steady-state performance of the overall vibration isolation device.

[0109] This invention further improves the magnetic field coupling efficiency, structural stability, and response consistency of each functional module by designing a multi-layer composite structure of the vertical conductive support plate 31 and the horizontal magnetic support plate 32, and by optimizing the structure and arrangement of the upper and lower eddy current stator assemblies 42. Simultaneously, based on the negative stiffness generation mechanism of air gap differential change, the system can generate an effective net restoring force through automatic adjustment of electromagnetic force when facing load fluctuations or external disturbances, thereby better maintaining a quasi-zero stiffness state.

[0110] See Figure 10 As shown, this structure can achieve the quasi-zero stiffness requirement in higher frequency bands. With the adjustment of the air gap d, the width of the quasi-zero stiffness frequency band continues to increase, verifying the significant superiority of this vibration isolation device in the field of low-frequency vibration isolation.

[0111] In a preferred embodiment, the electromagnetic quasi-zero stiffness vibration isolation device further includes a load support platform 5, which comprises a vertical support arm 51 and a horizontal support platform 52 mounted on the vertical support arm 51. The vertical support arm 51 is connected to the middle of the upper surface of the horizontal magnetic support plate 32, and the horizontal support platform 52 is used to support the load. At least one gravity sensor is also provided on the load support platform 5 for real-time detection of the weight of the currently loaded load. The gravity sensor is typically installed at the connection between the vertical support arm 51 and the horizontal support platform 52, or directly integrated into the internal structure of the horizontal support platform 52. Its measurement direction is preferably consistent with the direction of gravity to ensure the accuracy of the measurement results. The output signal of the gravity sensor can be transmitted to the controller in the system to obtain the weight information of the current load in real time. As one of the input parameters of the control algorithm, it assists the controller in dynamically adjusting the current of the linear induction motor assembly 2 and / or the eddy current stator assembly to adapt to the quasi-zero stiffness maintenance requirements under different load conditions.

[0112] Example 2

[0113] See Figure 11 The present invention also provides a control method for an electromagnetic quasi-zero stiffness vibration isolation device based on a composite nested structure as described in Embodiment 1, used to maintain and dynamically adjust the quasi-zero stiffness state of the device in the vertical direction. This control method dynamically adjusts the currents of the linear induction motor assembly 2 and the eddy current stator assembly through real-time monitoring and feedback control to ensure that the device maintains good vibration isolation performance under different load conditions; its steps include:

[0114] S1. Establish initial normal stiffness to stably support the load:

[0115] First, an initial alternating current is supplied to the three-phase AC windings 22 of the two linear induction motor assemblies 2, causing the motors to generate an upward electromagnetic repulsion force F. This electromagnetic repulsion force is used to balance the weight mg of the load, thereby achieving initial support for the load.

[0116] Specifically, the balance between the electromagnetic repulsive force F and the load gravity mg is monitored in real time using a force sensor;

[0117] Based on the monitoring results, the current amplitude of the three-phase AC winding 22 is finely adjusted until the balance condition F=mg is met.

[0118] At this point, the device establishes its initial positive stiffness, and the positive stiffness module, composed of the linear induction motor assembly 2 and the vertical conductive support plate 31, begins to stably support the load, and the system enters its initial equilibrium state.

[0119] S2. Establish initial negative stiffness and set air gap reference:

[0120] After the positive stiffness is established, an initial DC current is simultaneously applied to the upper eddy current stator assembly 41 and the lower eddy current stator assembly 42 in each pair of eddy current stators 4, so that the two generate a magnetic field and interact with the horizontal magnetic support plate 32 to form the initial negative stiffness.

[0121] Specifically, the mechanical air gap between the upper and lower eddy current stator assemblies 42 and the horizontal magnetic support plate 32 is fed back in real time by displacement sensors;

[0122] Based on the air gap feedback, the magnitude of the DC current is finely adjusted so that the horizontal magnetic support plate 32 is positioned in the middle of the upper and lower eddy current stator assemblies 42.

[0123] And ensure that both the upper and lower air gaps are the pre-set initial mechanical air gaps d, so as to provide a reference for subsequent negative stiffness adjustment.

[0124] S3. Real-time monitoring and dynamic adjustment to maintain near-zero stiffness:

[0125] During normal operation of the device, the vertical displacement x of the horizontal magnetic support plate 32 is acquired in real time by a displacement sensor, while the load change is acquired in real time by a force sensor. The two sensors feed back the acquired signals to the controller in real time.

[0126] The controller dynamically adjusts the current magnitude of the linear induction motor assembly 2 and / or the eddy current stator assembly based on the received displacement x and load information to maintain the quasi-zero stiffness state of the entire vibration isolation device.

[0127] The specific control strategy is as follows:

[0128] S31. When the load increases:

[0129] Positive stiffness adjustment: The controller increases the current of the three-phase AC winding 22 of the linear induction motor assembly 2, thereby enhancing the electromagnetic repulsion to support the new load and push the vertical conductive support plate 31 back to the static equilibrium position.

[0130] Negative stiffness adjustment: Simultaneously increase the DC current of the eddy current stator pair 4 to enhance the magnetic field effect and improve the electromagnetic force of the negative stiffness module;

[0131] Synergistic effect: Through synchronous adjustment, the positive stiffness and negative stiffness modules work together to maintain the quasi-zero stiffness state of the system under new load conditions.

[0132] When the load decreases:

[0133] Stiffness adjustment: The controller reduces the current in the three-phase AC winding 22 of the linear induction motor assembly 2, reduces the electromagnetic repulsion to accommodate the reduced load, and guides the vertical conductive support plate 31 back to the static equilibrium position.

[0134] Negative stiffness adjustment: Simultaneously reduce the DC current of the eddy current stator pair 4, reduce the magnetic field strength, and reduce the electromagnetic force of the negative stiffness module;

[0135] Synergistic effect: By coordinating the reduction, it ensures that the positive and negative stiffness modules can still maintain a near-zero stiffness state together after the load is reduced.

[0136] The control method provided by this invention dynamically controls the balance between the electromagnetic repulsion force F and the load gravity mg by adjusting the three-phase AC current in real time through the linear induction motor assembly 2, thereby achieving on-demand adjustment of the positive stiffness. Combined with the eddy current stator pair 4, the mechanical air gap d is adjusted via DC current to actively control the electromagnetic force of the negative stiffness module. The synergy of these two methods allows the device to maintain a quasi-zero stiffness state through current feedback adjustment when the load changes, thus solving the technical problem of the non-adjustable stiffness of traditional vibration isolation devices. This ensures that a quasi-zero stiffness state is maintained under multiple operating conditions, effectively suppressing low-frequency vibrations and improving vibration isolation performance. The composite nested structure decouples the positive and negative stiffness, allowing for independent current control to adapt to different load ranges. The eddy current effect of the negative stiffness module further reduces the system's natural frequency due to the lack of mechanical contact. Combined with the positive stiffness module, this effectively extends the vibration isolation frequency band, especially targeting low-frequency vibrations that are difficult to suppress with traditional devices. Real-time feedback from the displacement sensor and force sensor forms a dual closed-loop regulation, with the current adjustment accuracy directly related to the stiffness balance state. Compared to open-loop vibration isolators, this invention reduces stiffness drift caused by environmental interference and improves long-term operational reliability through a closed-loop link of sensor-controller-actuator (linear induction motor assembly 2 / eddy current stator pair 4).

[0137] The above are merely preferred embodiments of the present invention and do not limit the patent scope of the present invention. All equivalent structural transformations made using the contents of the present invention's specification and drawings under the inventive concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. An electromagnetic quasi-zero stiffness vibration isolation device based on a composite nested structure, characterized in that, include: Support base; Two linear induction motor assemblies are symmetrically arranged on the support base with a preset gap between them; The suspended support frame includes a vertical conductive support plate and a horizontal magnetic support plate, with the horizontal magnetic support plate located on top of the vertical conductive support plate; The vertical conductive support plate can float up and down within a preset gap, and together with two linear induction motor assemblies, it forms a positive stiffness module that provides the main support force and positive stiffness. Two pairs of eddy current stators are symmetrically arranged on the left and right sides of a horizontal magnetic support plate. Each pair of eddy current stators includes an upper eddy current stator assembly and a lower eddy current stator assembly that float mutually on the upper and lower sides of the horizontal magnetic support plate, and together with the horizontal magnetic support plate, they form a negative stiffness module that provides negative stiffness. The upper eddy current stator assembly and the lower eddy current stator assembly have the same structure, each including an eddy current stator core and several DC coil units disposed on the eddy current stator core, with each DC coil unit connected in parallel. The positive stiffness module and the negative stiffness module are arranged coaxially in the vertical direction and achieve quasi-zero stiffness characteristics through parallel collaboration of a composite nested structure. The horizontal magnetic support plate is also equipped with a displacement sensor, which is used to detect the vertical floating displacement of the suspended support frame and feed it back to the controller; The controller adjusts the current magnitude of the linear induction motor assembly and / or eddy current stator pair in real time based on the received vertical floating displacement to maintain the near-zero stiffness state of the vibration isolation device.

2. The electromagnetic quasi-zero stiffness vibration isolation device based on a composite nested structure according to claim 1, characterized in that, The linear induction motor assembly includes a stator core and a three-phase AC winding embedded in the stator core; An alternating current is passed through the three-phase AC windings, and the relatively arranged linear induction motor assembly generates a traveling wave magnetic field that interacts with the vertical conductive support plate to form a vertical electromagnetic thrust to provide the main support force and positive stiffness.

3. The electromagnetic quasi-zero stiffness vibration isolation device based on a composite nested structure according to claim 1 or 2, characterized in that, The vertical conductive support plate includes a vertical support plate body, vertical moving conductor conductive plates respectively attached to both sides of the vertical support plate body, and vertical moving magnetic conductive plates respectively attached to the outer side of the corresponding vertical moving conductor conductive plates.

4. The electromagnetic quasi-zero stiffness vibration isolation device based on a composite nested structure according to claim 1 or 2, characterized in that, The horizontal magnetic support plate includes a horizontal support plate body, a first upper moving magnetic plate and a second upper moving magnetic plate that are respectively spaced and attached to the upper surface of the horizontal support plate body, and a first lower moving magnetic plate and a second lower moving magnetic plate that are respectively spaced and attached to the lower surface of the horizontal support plate body. Furthermore, the upper moving element magnetic plate and the lower moving element magnetic plate are positioned in a matching manner. The upper moving part magnetic plate and the lower moving part magnetic plate are positioned in a matching manner.

5. The electromagnetic quasi-zero stiffness vibration isolation device based on a composite nested structure according to claim 1 or 2, characterized in that, The electromagnetic quasi-zero stiffness vibration isolation device also includes a load support platform, which includes a vertical support arm and a horizontal support platform mounted on the vertical support arm. The vertical support arm is connected to the middle of the upper surface of the horizontal magnetic support plate, and the horizontal support platform is used to support the load; and the load support platform is equipped with a gravity sensor to detect the weight of the load.

6. The electromagnetic quasi-zero stiffness vibration isolation device based on a composite nested structure according to claim 1 or 2, characterized in that, The support base includes a base plate and two vertical plates vertically arranged on the base plate, with the two vertical plates spaced apart. A linear induction motor assembly is disposed on the inner side of a vertical plate; Another linear induction motor assembly is correspondingly disposed on the inner side of another vertical plate, so that the two linear induction motor assemblies are arranged opposite each other.

7. A control method for an electromagnetic quasi-zero stiffness vibration isolation device based on a composite nested structure as described in any one of claims 1-6, characterized in that, The steps include: S1. Initial alternating current is passed through the three-phase AC windings of the two linear induction motor components to generate an upward electromagnetic repulsion force F. The force sensor monitors the balance between F and the load gravity mg and finely adjusts the current to F=mg to establish initial positive stiffness to stably support the load. S2. Initial DC current is passed into the upper and lower eddy current stator assemblies of each pair of eddy current stators. The mechanical air gap is fed back by the displacement sensor and the current is finely adjusted so that the horizontal magnetic support plate is located between the upper and lower eddy current stator assemblies and the preset air gap d is maintained. S3. The displacement sensor acquires the vertical displacement x of the horizontal magnetic support plate in real time, and the force sensor collects the load change in real time and feeds it back to the controller. The controller adjusts the current of the linear induction motor assembly and / or the eddy current stator pair in real time according to x and the load to maintain a quasi-zero stiffness state.

8. The control method according to claim 7, characterized in that, In step S3, when the load increases, the electromagnetic repulsion of the positive stiffness module is increased by increasing the three-phase AC winding current of the linear induction motor assembly to support the new load and return the vertical conductive support plate to the static equilibrium position; at the same time, the DC current of the eddy current stator pair is increased to enhance the electromagnetic force of the negative stiffness module, and together with the positive stiffness module, they maintain a quasi-zero stiffness state. When the load decreases, the electromagnetic repulsion of the positive stiffness module is reduced by decreasing the three-phase AC winding current of the linear induction motor assembly to support the reduced load and return the vertical conductive support plate to its static equilibrium position; at the same time, the DC current of the eddy current stator pair is reduced to reduce the electromagnetic force of the negative stiffness module, and together with the positive stiffness module, the quasi-zero stiffness state is maintained.

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